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Seasonal Climate Forecast Dec. 2014 – Feb. 2015 (Issued: November 24, 2014)

Seasonal Climate Forecast Dec. 2014 – Feb. 2015 (Issued: November 24, 2014). This Product is Published by the Oregon Department of Agriculture (ODA), in Cooperation with the Oregon Department of Forestry (ODF). Contact: ODF Meteorologist Pete Parsons

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Seasonal Climate Forecast Dec. 2014 – Feb. 2015 (Issued: November 24, 2014)

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  1. Seasonal Climate ForecastDec. 2014 – Feb. 2015(Issued: November 24, 2014) This Product is Published by the Oregon Department of Agriculture (ODA), in Cooperation with the Oregon Department of Forestry (ODF). Contact: ODF Meteorologist Pete Parsons at 503-945-7448 or peter.gj.parsons@oregon.gov Get related Seasonal Climate Forecast information at: http://www.oregon.gov/ODA/programs/NaturalResources/Pages/Weather.aspx

  2. Forecast Method Notes… • Analog years were obtained by tracking and comparing a variety of indices over the past several years (see Forecasting Methods). Priority was given to years from a “Cool Phase”period of the Pacific Decadal Oscillation (PDO) with sea-surface temperatures (SSTs) most closely matching the current SSTs in the equatorial Pacific Ocean. • The analog years (2009-10; 1968-69; 1951-52) used to create this forecast are all from “Cool Phase”periods of the “PDO” and are unchanged from last month. • A moderate-strength El Niño developed during the winter in each of the top analog years.

  3. El Niño Southern Oscillation (ENSO)Current Status and Forecast • ENSO-neutral (average) conditions continue across the equatorial Pacific Ocean, although sea-surface temperatures (SSTs) are above weak El Niño thresholds. • The Climate Prediction Center’s (CPC) confidence in the development of a full-fledged El Niño…lasting into the spring of 2015, has dropped but is still above 50%. • The “analog years” used in this forecast support the development of a moderate-strength El Niño this winter. • A weak or moderate-strength El Niño is most likely for this coming winter, but continued warm ENSO-neutral conditions is also possible. http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

  4. Tropical Pacific OceanAnimated (in PowerPoint only) SSTs (top) / Anomalies (bottom) Courtesy: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/sstanim.shtml

  5. Tropical Pacific OceanSSTs have warmed into the range of a weak El Niño Courtesy: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/sstweek_c.gif

  6. ENSO Indices (2008-09;1967-68; 1950-51) La Niña ENSO-Neutral El Niño

  7. ENSO Indices (2008-09;1967-68; 1950-51) El Niño developed, by late-autumn, in each of the top 3 analog years. El Niño ENSO-Neutral El Niño may develop this winter. La Niña conditions developed, during the winter, in 1 of the top 3 analog years. La Niña

  8. ENSO Predictive ModelsComputer models favor a weak El Niño this winter Model forecasts favor ENSO-neutral conditions through spring 2014; followed by El Niño development. El Niño ENSO-neutral La Niña Courtesy: http://iri.columbia.edu/climate/ENSO/currentinfo/SST_table.html

  9. December 2014 Forecast Temperatures Precipitation • Consensus among the analog years is for below average temperatures. • Two of the top analog years (1951 & 1968) were very stormy with above average precipitation, but the third year (2009) was quite dry. • Heavy valley snow in December 1968 but not in 1951 nor in 2009.

  10. January 2015 Forecast Temperatures Precipitation • Extreme variation of weather among the analog years…ranging from very cold and wet (1969) to very mild and somewhat dry (2010). • Graphics are skewed cold and wet by the extreme conditions of 1969, but a mild and dry January is more typical with El Niño.

  11. February 2015 Forecast Temperatures Precipitation • Extreme cold is unlikely, but overall temperatures may end up below average (not typical of El Niño). • Precipitation near or below average (more typical of El Niño).

  12. Dec. 2014 – Feb. 2015 Forecast Temperatures Precipitation • Tremendous variation among analog years for December and January increases forecast uncertainty. A “classic” El Niño produces warmer and drier than average weather, but the opposite extremes can occur…

  13. Dec. 2014 – Feb. 2015 Highlights • A weak or moderate El Niño is likely this winter, which commonly produces cool and stormy conditions in late-autumn, but relatively mild and dry weather in mid-winter. • Mountain snowfall (relative to average) is typically greater across southern Oregon than across northern Oregon. • However, there are other possibilities… • In stark contrast to the current Climate Prediction Center (CPC) Forecasts, the analog method used here shows that extremely cold and wet weather can’t be ruled out for December and January. • Dec. 1968 – Jan. 1969, (one of the top analog years) produced multiple Arctic outbreaks with heavy snowfall across much of the state, especially for northern Oregon. • Extremely cold weather becomes unlikely after January, but generally cool temperatures may prevail into February.

  14. Some Helpful Resources • CPC Official US Three-Month Forecasts (Graphics): http://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal.php?lead=01 • CPC US 30-Day & 90-Day Forecasts (Discussions): http://www.cpc.ncep.noaa.gov/products/predictions/long_range/fxus07.html • CPC Weekly & Monthly ENSO Discussions: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory • Australian Government Weekly Tropical Climate Note: http://www.bom.gov.au/climate/tropnote/tropnote.shtml • Australian Government ENSO Wrap-Up: http://www.bom.gov.au/climate/enso • IRI ENSO Quick Look: http://portal.iri.columbia.edu/portal/server.pt?open=512&objID=945&mode=2 • NRCS Western Snowpack Data & Water Supply Forecast: http://www.wcc.nrcs.usda.gov/cgibin/westsnowsummary.pl

  15. Updated Monthly(around the 20th) Your Feedback is Welcome Contact: Pete Parsons, ODF Meteorologist at 503-945-7448 or peter.gj.parsons@oregon.gov ODA Production support from Diana Walker and Andy Zimmerman

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